This application claims priority to Japanese Patent Application No. 2000-100844 filed in Japan on Apr. 3, 2000, the contents of which are hereby incorporated by reference.
The present invention relates to a glass composition, and specifically relates to a glass composition suited for crystallized glass. More specifically, the present invention relates to a composition for crystallized glass disk medium. Such disk medium include hard disks, magnetic disks, optical disks and magnetic-optical disks
Aluminum and glass are known materials suitable for use as magnetic disk substrates. Among these substrates, glass substrates have been the focus of most attention due to their superior surface smoothness and mechanical strength. Such glass substrates include chemically reinforced glass substrates strengthened by ion exchange on the surface, and crystallized glass substrates having strengthened bonds by depositing a crystal component on the substrate.
The performance demands of recent substrates have become more severe day by day, and improved performance is particularly sought regarding strength, flex and warp during high-speed rotation. This type of performance can be expressed by the Young""s modulus of the substrate material, in which a higher numerical value is desirable.
For example, the composition disclosed in Japanese Laid-Open Patent Application No. 11-322362 attains a Young""s modulus value of 130 or greater. However, this prior art requires extremely high thermal processing temperatures which complicate the manufacturing process, that is, this art requires a primary processing temperature of 800xc2x0 C., and a secondary processing temperature of 1,000xc2x0 C.
An object of the present invention is to provide an improved glass composition.
Another object of the present invention is to provide a glass composition having a high Young""s modulus and which is highly suited for mass production.
These objects are attained with a glass composition of the present invention desirably having the main components within the ranges described below:
about 35 wt % or more, but less than about 50 wt % SiO2;
about 5 wt % or more, but less than about 30 wt % Al2O3;
about 20 wt % or more, but less than about 22 wt % MgO; and
about 5 wt % or more, but less than about 12 wt % TiO2.